Speed controlled brake



Sept. 17, 19.40. B s` AlKMAN 2,215,343

SPEED CONTROLLED BRAKE sept. 17, 1940. B, s MKMAN 2,215,343

SPEED CONTROLLED BRAKE Filed July 29, 1939 3 Sheets-Sheet 2 :as s te:

O 200 E03 204 ISO vlNvlsN'roR BURTON S. AlK MAN ATTORNEY Sept. 17, 1940.

B. s. AIKMAN SPEED coNTRoLLED BRAKE Filed July 29, 1939 3 Sheets-Sheet 3 www -\\\\NWN mmm ow 00m. mm m\ m vm Nm -Patented Sept. 17, 1940 UNITED STATES PATENT OFFICE SPEED CONTRLLED BRAKE Application July 29, 1939, Serial No. 287,274

Claims.

This invention relates to uid pressure brakes and more particularly to iiuid pressure controlled speed responsive apparatus operative to govern the degree of application of the brakes for preventing wheel sliding.

It is common knowledge that in order to stop a moving vehicle within a desirably short distance, it is necessary that all wheels be permitted to roll freely while decelerating in response to an application of the brakes, and that for production of maximum braking eifect the wheels should consequently at'all times be subjected to braking friction just short of that sufcient to cause slipping. The force with which the brakes are applied must therefore be gradually reduced to correspond with the changing coeiicient of friction between the brake shoes and wheels, it being understood that the latter frictional force increases as the vehicle speed declines.

One object of my invention is to provide an improved uid pressure controlled apparatus automatically operative according to the speed of a vehicle to limit the pressure of fluid attainable in the brake cylinder of the vehicle air brake system to a value producing maximum braking effect Without causing wheel slipping.

It is another object of the invention to provide an apparatus of the above description which is suii'iciently sensitive to abnormal or sudden reduction in the rotative speed of a, vehicle Wheel, resulting from initial slipping thereof, to effect a quick release of braking force before the wheel ceases rotating, thereby preventing sliding of the wheels.

A further object of the invention is to provide a speed controlled, anti-wheel sliding apparatus governed in response to Variations in a control pressure, which pressure is in turn determined during a brake application by the rate at which 40 a constantly replenished supply of fluid under pressure is discharged to atmosphere through a calibrated port of a valve device operated by the vehicle wheel.

Other objects and advantages of the invention will be apparent in the following description thereof, taken in connection with the accompanying drawings, in which: v

Fig. 1 is a diagrammatic elevational view, mainly in section, of a speed responsive iiuid pressure brake control apparatus embodyingfeatures of the invention;

Fig. 21 is an end view, partly in section and taken substantially along the line 2-2 of Fig. 1;

Fig. 3 is a diagrammatic elevational View, mainly in section, showing a 'different formv of the control apparatus embodying the invention; A

Fig. 4 is a sectional View taken substantially on the line 4-4 of Fig. 3;

Fig. 5 is a fragmentary sectional view taken substantially on the line 5 5 of Fig. 3; and

Fig. 6 is a diagrammatic elevational view, mainly in section, of a fiuid pressure control apparatus embodying features of the invention instill another form.

Apparatus shown in Fig. 1

As shown in Fig. 1 of the drawings,` one form of apparatus embodying the invention and associated portions of a vehicle truck may comprise a brake cylinder device Il), which is operative through the medium of suitable brake levers, not illustrated, to apply braking force to a wheel II having an axle I2, a control valve device I3 associated with the brake cylinder device, and a control pressure governor mechanism operatively mounted on the axle and indicated generally by the character I5.

'Ihe brake cylinder device I may be of usual construction and as illustrated comprises a cylinder within which is slidably mounted a piston I 'l subject to the pressure of fluid supplied to a pressure chamber I8 for operating a piston rod I il against the force of a coil spring 20, which is dis.- posed in a normally vented chamber 22. brake cylinder device has a bracket wall 2l, `to the outer surface of which the control valve device I3 may be secured by bolts, not shown. A relay valve -device 22 is provided for supplying fluid under pressure t'o the brake cylinder chamber I8 from a constantly charged supply pipe 28, which communicates with the usual main reservoir, not shown. The relay valve device may be similar to that disclosed in the United States Patent 2,096,491 issued October 19', 41937, tof E'. E. Hewitt.

The control valve device I3 comprises a casing The structure having formed therein a valve cham-` ber 23 which communicates through a port 2li formed in thewall 2| with the piston bore .of the brake cylinder device Il), which port 24 is adapted to be uncovered by the brakecylinder piston Il I upon movement thereof to a brake applying position as hereinafter explained. Mounted in the valve chamber 23 is a valve member 25, which is adapted to be held in seating engagement with a seat rib 26 formed in the casing under the forcel of a coil spring Z'I which is interposed betweenivry the valve and the wall of the chamber 23.` The vvaive 25 has a. cured stem'poruon 29 5nd bly mounted in a bore 30 formed in the casing, the lower end of which stem is secured to a loosely fitted piston 3l which is interposed between a piston chamber 33 and a chamber 34 communicating by way of a passage35 and a port 38 with the piston bore of the brake cylinder device I 8. The port 88 is located in the wall 2| of the brake cylinder device beyond the range of movement of the piston I1. The chamber 34 is at all times connected with the atmosphere by way of suitable ports 38, and is adapted to be cut off from communication from the bore 3|! upon upward movement of the piston 3| by means of a'gasket 40 which is adapted to seat on a rib 4| surrounding the bore.

The valve chamber 23 also communicates by way of a passage 44 with a chamber 45 formed in the casing and containing a needle valve element 48, which is adapted to be operated by a flexible diaphragm 48 that is interposed between the casing and a cap member 49 suitably secured thereto.- A coil spring 5|A is interposed between the end wall of the cap member 49 and a follower member 52 engaging the diaphragm 48, and is adapted normally to act through the medium of the diaphragm tohold the needle valve element 45 in seated position as shown in the drawings. The diaphragm 48 is adapted to respond to a predetermined increase in iiuid pressure in chamber 45 to operate the needle valve element .45 for eifecting supply of fluid under pressure from the chamber to a passage 54 having va restricted portion 55, the needle valve element being thus adapted to maintain a substantially uniform now of fluid under pressure through the passage 54 as hereinafter more fully explained.

Communication from the valve chamber 23 to the chamber 33 is controlled by a valve element 51, which is interposed in a passage 58 formed in the casing of the device I3, and has a stem portion suitably secured to a diaphragm 80 that is mounted in the casing and is interposed between a chamber 6| and a chamber 02 communicating with the passage 54. A follower element 65 is i mounted in engagement with the side of the diaphragm opposite the valve element 51 and is provided with a restricted passage 88 forming communication between the chambers 6| and 62. A

coil spring 61 is interposed between the followez' element 65 and the wall of the chamber 6| for acting on the diaphragm in opposition to the pressure of fluid in the chamber 62 and for normally maintaining seated the valve element 51. The chamber 8| communicates by way of a passage 68 with a volume chamber 69 and is adapted at times to communicate with the valve chamber 23 by way of a passage 10, which 'is normally maintained closed by a valve member 1| that is disposed in a Valve chamber 12 communicating with the passage. The valve member 1| is carried by a piston 14, which is mounted in a suitable bore formed in the casing and is subject to the pressure of uid supplied to the chamber 12 and to the opposing force of a spring 15 contained in a volume chamber 16, which communicates assembly.

The control pressure governor mechanism I5 is adapted to o-perate in accordance with the speed of rotation of the wheel and axle assembly to control the pressure of fluid supplied to the conduit 80, said uid pressure being maintained at a minimum Value while the axle is operated at high speed, and at correspondingly increased values during deceleration of the axle as hereinafter eX- plained. The governor mechanism I5 comprises, in addition to the member 82, a torque arm member 84, which has an arm portion 85 operatively connected to a bracket 8S carried by a portion 81 of the vehicle frame, and an arcuate portion 88 adapted to be disposed above the axle I2. An arcuate bearing member 9| formed of self-lubricating carbonaceous material is secured within the semicircular portion 88 of the member 84 by means of pins such as 92, and has the inner surface thereof suitably formed for engagement with an annular member 93, which is in turn pressfitted on or otherwise suitably secured to the axle I2. Formed on the semicircular portion 88 of the member 84 and disposed at opposite sides of the axle are ange portions 95, which are adapted to be fitted with bolts 96 for supporting a pair of downwardly extending guide members 91, respectively, the inner surfaces of which are spaced from the annular member 93.

The member 82 is provided with oppositely extending arm portions 99 respectively disposed beneath the members 91, and has mounted thereon between the arm portions a Valve seat block which is preferably formed of a carbonaceous material similar to that of the bearing member 9 I. Suitable means such as screws |02 may be provided for holding the Valve seat block |0| in place. The block |0| is slidably fitted between the lower ends of the guide members 91 and is provided with a curved bearing face |04 adapted for sealing and sliding engagement with a ring element |09 secured to the annular member 93. The member 82 and the valve seat block |0| carried thereby are yieldingly supported from the respective guide members 91 by a plurality of tension springs |05, the lower ends of which are secured to the arm portions 99 of the member 82 and the upper ends of which are connected to eyelet portions |01 formed on the guide members. The springs are adapted to exert sufcient upward force on the member 82 to maintain the surface |04 of the block |0I in sliding engagement with the annular member 93 at all times.

The annular member 93 has formed therein a plurality of circumferentially spaced chambers or cavities |08, the outer ends of which are covered by the ring element |09, which is closely tted on and forms a part of the annular member. Restricted ports III are formed in the ring element |09, each of which ports communicates with one of the cavities |08. During rotation of the axle and of the member 93 carried thereby, the ports are adapted to be brought successively into registration with a passage ||2 formed in the block |0| and communicating with the chamber 8| and conduit 80.

It should be understood that the fluid pressure brake equipment associated with the brake cylinder device I0 but not shown in the drawings is of the high speed type, and is operative in effecting an application of the brakes to supply fluid to the chamber |8 at a pressure predetermined in accordance with the desired degree of brake application.

Fluid under pressurethus supplied to the brake cylinder device may be delivered directly from a main or other relatively large reservoir supply by operation of the relay valve device 22 in the usual manner, so that the amount of uid under pressure available for operation 'of the brake cylinder device is large enough to compensate for the use of a relatively small quantity of such fluid for operation of the speed controlled apparatus shown in Fig. 1, as hereinafter explained.

When iiuid under p-ressure is thus supplied to the piston chamber |8 in order to effect an application of the b-rakes, the piston l1 is moved against the opposing force of the spring 20 for causing the piston rod I9 to operate the usual brake rigging levers to apply braking force to the associated wheel and axle assembly. As the piston is moved to the right in the brake cylinder to a position corresponding to the application of an eifective braking force to the wheels, the port 24 in the lower wall 2| of the brake cylinder is uncovered and a communication thus established through which iiuid under pressure is supplied from the chamber I8 to the valve chamber 23. Upon the initial charging of the valve chamber 23, fluid under pressure ilow therefrom through the passage 'l0 to the chamber 'l2 at a rate faster than that of flows therefrom through the restricted port I8 in the piston 14, and thereby forces the piston downwardly against the pressure of the spring T5 for unseating the valve 1|, whereupon fluid under pressure is admitted to the diaphragm chamber 6| and b-y way of the passage 68 to the volume chamber 69.

At the same time, fluid under pressure flows from the valve chamber 23 through the passage 44 to the chamber 45, and acts against the diaphragm 48 in opposition to the force exerted by the spring 5|. Assuming that brake cylinder pressure has been increased to a predetermined value corresponding with the power of the spring 5|, the fluid pressure in chamber 45 then forces the diaphragm 68 outwardly for moving the needle valve member 46 awa-y from its seat. Fluid under pressure is then supplied from the chamber l5 past the unseated needle valve to the passage 5 at a rate determined by the restricted portion 55, and thence through the conduit to the chamber 8| in the member 82 of the governor mechanism associated with the wheel and axle.

From the chamber 8| fluid under pressure is intermittently discharged by flow through the passage ||2 and ports into the respective cavities |08 of the annular member 63, which revolves with the wheel and axle, as the ports are rapidly carried into and out of registration with the passage H2. Each of the cavities |08, being of relatively small volume, is thus charged with fluid at substantially the pressure of that in the conduit 60 and passage ||2, and as each cavity is subsequently carried beyond the block |0| the fluid under pressure entrapped therein is free to flow through the port to the atmosphere.

It will thus be seen that, due to the substantially constant supply of uid under pressure from the brake cylinder to the passage 54 of control valve device |3 eiected by operation of the diaphragm 48 and needle valve 46, a fluid pressure is maintained in the connected chamber 62 and conduit 80, which pressure is in large part determined by the frequency with which fluid under pressure is discharged from the conduit through the passage |2 in block |0| to the cavities |08 in the annular member 93 revolving with the vehicle wheel. Assuming that the application of the brake has been effected While the ve,- hicle is traveling at a high rate of speed, in excess of 60 miles per hour for example, the venting of fluid under pressure from the conduit by way of the passage ||2 into the cavities |08, as they are moved into and out of registration with the passage in rapid succession, is effective to reduce the Iiuid pressure in the conduit and in the chamber 62 to a relatively low value.

At this time, the fluid under pressure in the volume chamber 60 and in the chamber 6| is free to flow therefrom through the restricted passage 66 in the diaphragm 60 to the chamber 62. The fluid pressure in the chamber 6| is thus substantially equalized with that in the chamber 62, while the valve 5l is of course held in seated position as shown in the drawings under the pressure of the spring 61.

As the wheel and axle assembly subsequently begins to decelerate as result of the 'application of the brakes, the corresponding reduction in the frequency with which the cavities |08 in the axle carried member 03 are brought into registration with the passage ||2 is effective to permit a gradual increase in the pressure of fluid in the conduit 86, by reason of the continued. flow of fluid under pressure thereto past the needle valve 46 and through the restricted portion 55 of the passage 54 as hereinbefore explained.

It should be understood that the flow capacity or restricted portion or choke 55 is greater than that of the restricted passage 66 iln the diaphragm 60, but that the restricted passage 66 is of such size as to permit fluid under pressure to iow therethrough from the chamber 62 to the chamber 6| at a sufliciently fast rate, under normal conditions, to prevent establishment of an appreciable diferential between the pressuresV acting on opposite sides of the diaphragm 60. Thus while the wheel is decelerated at a rate not endangering slip-ping thereof, the spring 61 remains effective to hold the valve 5l in seated l position as shown in the drawings.

If the wheel should begin to slip, however, so that the rate of deceleration thereof is suddenly increased to an abnormal degree, the pressure of fluid in 'the conduit 86 and in the connected chamber'V 62 will consequently be suddenly increased, due to the fact that relatively little iluid under pressure is at this time withdrawn by way of the cavities |08 in the member 03 of the control pressure governor mechanism |5, while fluid under'pressure is still supplied from the brake cylinder by the usual operation of the needle valve 46 through the passage 54 to the chamber. The restricted passage 46 in the diaphragm 60 is calibrated to provide such a flow area as to prevent the passage of sufficient uid under pressure from the chamber 62 to the chamber 6| to effect the same rapid increase in fluid pressure in the chamber 6| as has thus been effected on the opposite side of the diaphragm, with the result that the diaphragm is moved against the force of the spring 61 to unseat the valve 5l'.

Fluid under pressure is then quickly supplied from the brake'cylinder by way of the port24, chamber 23, past the unseated Valve 25, and through passage 58 to the chamber 33, and acts through the medium of the piston 3| and stem 29 to move the valve 25 away from the seat 26, whereupon fluid under pressure is admitted from the chamber 23 through the bore 30, passage 35, and port 36 to the chamber 22 on the outer or spring side of the brake cylinder piston I1. Upon the consequent equalization of the iluid pressures acting on opposite sides of the brake cylinder piston, the braking force previously exerted thereby is immediately reduced sufficiently to l permit the wheel I to resume normal rotation at the speed corresponding to vehicle speed. It will be noted that when the piston 3| is moved to its uppermost position, the communication from the bore to the chamber 34 and atmospheric exhaust ports 38 is cut 01T, because of sealing engagement by the gasket with the seat rib 4|.

As the speed of rotation of the wheel is thus restored to a value corresponding with the speed of the vehicle, the annular member 93 is again operated by the axle I2 to effect a reduction in the pressure of fluid in the conduit 80 and in the chamber 62 connected thereto, in the manner already explained, and since the continued flow of fluid under pressure from that chamber through the restricted passage 66 to the chamber 6| has meanwhile somewhat increased the fluid pressure therein, the spring 61 is once more enabled to move the diaphragm 60 to the right for seating the valve 51. With the communication from the brake cylinder by way of the passage 58 to the chamber 33 thus cut off, the uid under pressure entrapped therein is quickly vented due to flow of uid past the loose tting piston 3| to the chamber 34 and atmospheric exhaust ports 38. The spring 21 is thereby rendered effective to force the valve 25 downwardly into engagement with the seat rib 26 for cutting off communication between the chamber 23 and the several communications leading to the chamber 22 at the outer side of the brake cylinder piston I1. Reapplication of the brakes is then automatically elected, assuming that the piston chamber I8 is still in communication with the uid pressure supply through operation of the relay valve device 22 by the usual brake controlling device, not shown in the drawings. It is preferred that the parts be so designed and adjusted that the full reapplication does not take place before the wheel has returned to substantially that corresponding to vehi-cle speed.

It will now be apparent that, with the speed controlled anti-wheel sliding equipment just described, automatic control of an individual wheel of a Vehicle during an application of the brakes is insured. According to the invention the anti- Wheel slide apparatus is adapted to be operated entirely by uid pressure, and may thus be employed with an existing iiuid pressure brake equipment Without the necessity of expensive a1- ternations.

Apparatus shown in Fig. 3

Illustrated in Fig. 3 of the drawings is a speed controlled equipment for a fluid pressure brake constructed in accordance with a modi'ed form of the invention, the equipment shown comprising a wheel and axle assembly |20, a brake cylinder device |2| of usual design, a main reservoir or other reservoir adapted to be maintained charged with a substantially constant supply of uid under pressure, indicated at |22, a cut 01T valve device |23, a control valve device |24, and a control pressure governor mechanism I 25.

The brake cylinder device |2| comprises a cylinder having a piston chamber |30 adapted to be supplied with fluid under pressure by way of a pipe and passage I3 which cylinder has mounted therein a piston |32 subject to the pressure of fluid in the chamber |30 and operative through the medium of a piston rod` 33 to effect an application of the brakes.

The supply of uid under pressure to the chamber |30 of the brake cylinder device is in part controlled by operation of the cut-off valve device |23, which comprises a casing having an inlet chamber |36 communicating through a pipe |35 with the usual brake controlling valve devices, not shown, and also having an outlet chamber |31 communicating with the chamber |36 and with the pipe |3|. Mounted within the casing of the cut-off valve Idevice |33 is a rubber diaphragm valve |39 which is adapted for cooperation with a seat |40 for controlling communication between the chambers |36 and |31. A diaphragm |42 is mounted in the lower portion of the casing of the device |23 and is operative upon a predetermined increase in the pressure of fluid in a chamber |43 to close the diaphragm valve |39 through the medium of a follower element |44 interposed between the two diaphragms. A check valve |4|, interposed between the chambers |31 and |36, is provided to permit release flow of fluid from the brake cylinder device at all times.

The control valve device |24 includes a casing structure having a valve chamber |48, which is connected through a pipe |49 with brake cylinder chamber |30, and in which is disposed a release valve element |50 controlling communication from the valve chamber by way of a bore |5| and chamber |52 to an atmospheric exhaust port |53 formed in the casing. The valve element |50 is normally urged against a seat |54 under the predetermined force of a spring |56, interposed between a cap member |51, which is adjustably secured in the casing, and a diaphragm which engages the valve element |50 and is subject to the pressure of fluid in the chamber |48. The Valve |50 is also controlled through the medium of a stem |60 and follower member |6| by a diaphragm |63, which is mounted in the casing structure between the chamber |53 and a pressure chamber |65 communicating through a pipe |66 with the chamber |43 of the cut-oli valve device |23.

The chamber |65 of the control valve device |24 is also connected to one end of a conduit |61 leading to the pressure governor mechanism |25, hereinafter described. For maintaining a substantially constant supply of fluid under pressure to the chamber |65, a feed valve element |10 is disposed in a chamber |1| communicating through a restricted passage and pipe |12 with the reservoir |22, which valve element is urged toward a seat |14 under the force of a spring |15 and controls communication from the chamber |1| to a passage |16 connected to chamber |65. The feed valve element |10 has a fluted stem |11 which extends through the passage |16 and terminates in a valve portion |18 that is normally held in unseated position and controls communication from the passage |16 to an atmospheric exhaust port |19. The outer end of the valve portion |18 is engaged by a plunger |80, which is slidably mounted in the casing structure and is biased away from the valve portion |18 by the force of a spring |82. The plunger is movable in opposition to the force of the spring |82 by a diaphragm |83 upon a predetermined increase in the pressure of uid in a chamber |84, which communicates through a passage |85 with chamber |48.

The control pressure governor mechanism |25 is adapted to perform the same function as does the mechanism |5, shown in Fig. l and already described, although the two governor mechanisms differ in details of construction. The governor mechanism |25 includes a casing member |90 which is bolted or otherwise secured to a journal box structure, indicated generally by the character ISI, which is carried by the Wheel and axle assembly |20. The journal box structure |9| is illustrated as comprising a plurality of ball bearing assemblies |93 interposed between an axle portion |20a extending outwardly of the wheel, and a bearing member |94 suitably mounted in the corresponding side frame member of the truck, which the journal box structure is adapted to support through the medium of suitable springs, such as that indicated by the character |95. It will be understood that the Wheel and axle assembly |20 is thus rotatably mounted on the journal box structure |9|, which is stationary.

Slidably mounted in a bore 200 formed in the casing member |90 is .a valve block member 20| formed of self-lubricating carbonaceous material, which may be cylindrical in form and is prevented from turning in the bore by sui-table means, such as a longitudinal groove 202 provided in the outer surface of the block and adapted to receive alpin 203 carried by the casing member. The block member 20| extends into a central chamber 205 formed within the casing member |90 and communicating, with an atmospheric opening 204, and has a reduced offset portion 20B on which is formed a flat sealing surface disposed in a plane parallel to that of thewheel |20. A calibrated or restricted passage 208 is formed within the valve block member 20| and communicates with the chamber 209 formed at the outer end of the block. For preventing leakage of fluid under pressure from the chamber 209 past the block 20|, a gasket 2| is secured to the outer end of the block by means of a follower plate 2|2 and a screw 2|3 which is fitted through suitable apertures in the follower member and gasket and into a screw threaded bore in the block member. A coil spring 2|5 is interposed between the inner wall of the chamber 209 and the follower member 2|2 for urging the valve block member 20| toward the wheel and axle assembly.

The sealing surface formed on the portion 206 of the block is adapted to engage a flat sealing surface 2|1 formed on a circular casing element 2|8, which is secured to the end of the axle portion |20a by suitable means, such as pins 2|9 and thus in eiect constitutes an extension of the axle. Formed in the member 2|8 are a plurality of spaced cavities or chambers 22|, each of which communicates with a port 222 opening at the surface 2|1 of the member and adapted forl registration with the restricted passage 203 in the block member 20|, each of the ports being so spaced from the center of the member 2|8 that during a revolution of the member each port will momentarily communicate with the passage 208 and then with the atmosphere. In Fig. 3 one of the ports 222 is shown positioned in communication with a restricted passage 208; in Fig. 5 two o-f the passages 222 are illustrated in their atmospheric exhaust positions.

It will be understood that when the equipment justdescribed is conditioned for operation, the reservoir |22 is charged with uid under pressure by means of a compressor, not shown, and that the brake cylinder pipe |35 is connected to the atmosphere through the usual communications in the brake controlling valve device or triple valve device forming part of the air brake equipment but not included in the drawings. At the same time, the vseveral valves and other movable parts of the speed controlled apparatus shown in Fig. 3 occupy the positions illustrated.`

Let it now be assumed that while the vehicle is traveling at a high speed and the wheel and with the axle.

axle assembly |20 is consequently revolving rapidly, the brake controlling valve device of the air brake system is operated in the usual manner to supply uid under pressure to the brake cylinder pipe |35 for effecting an application of the brakes. Fluid under pressure thus supplied by way of the pipe |35 flo-ws through the chamber |36 and past the diaphragm valve |39 of the device |23 and thence by way of chamber |31 and pipe |3| to the brake cylinder chamber |30, causing movement of the piston |32 and rod |33 to the right for forcing the usual brake shoes against the wheel. Fluid under pressure also flows from the brake cylinder chamber |30 through pipe |49 to the chamber L|40 of the control valve device |24, and thence by way of passage |85 to diaphragm chamber |84.

Upon a predetermined increase in the pressure of brake cylinder uid in the chamber |84, which predetermined pressure may be that usually attained during a service application of the brakes, the diaphragm |80 is forced against the pressure of the spring |82 to move the valve member |18 to its seated position while moving the valve element |10 away from the seat |14. Fluid under pressure is then fed from the reservoir |22 at a rate controlled by the restricted passage |12 past the unseated valve element |10 and through passage |16 to the chamber |65, from which fluid under pressure ows through the pipe |66 to the chamber |43 of the cut-01T valve device |23, and also through the conduit |51 to the chamber 209 of the control pressure governor mechanism |25 associated with the wheel and axle assembly.

Fluid under pressure thus substantially cnstantly supplied through the conduit |01 to the chamber 209 flows therefrom through the restricted passage 208 in the Valve block 20| to each of the ports 222 and the respective chambers 22| in succession, as the member 2|8 is revolved The chambers 22| are thereby momentarily charged with fluid under pressure from the chamber 209 and conduit |61 during each revolution of the axle assembly, the'volume of fluid under pressure received by each chamber being Vented therefrom as the chamber is moved to the position as shown in Fig. 5. As hereinbefore explained in connection with the pressure control governor mechanism I5 shown in Fig. 1,

the pressure of fluid in the conduit |61 is determined by the speed of rotation of the wheel and axle assembly, and will be at a minimum value while the vehicle is traveling at maximum speed, due to the frequency with which the metered volumes of fluid are withdrawn from the constantly supplied conduit.

It will thus be understood that the fluid pressure in the chamber of the control valve device |24 communicating with the conduit |61 is relatively low, during the initial application of the brakes While the vehicle is moving at high speed. Meanwhile, the fluid at the pressure of that of the brake cylinder in the chamber |48 is effective on the diaphragm |58 to oppose the force of the spring |56, so that the downward pressure tending to maintain seated the valve element |50 is reduced, but it lwill be understood that so long as the pressure of fluid inthe chamber |05 remains at a low value corresponding to high vehicle speed, the valve element |50 is held in engagement with the seat |54.

It is to be expected that, upon the application of the brakes as just described, the speed of the vehicle will quickly begin to reduce, thus necessitating corresponding reduction in the pressure of fluid in the brake cylinder |2| in order to prevent the application of too great a braking force with respect to the speed of the vehicle, such as might result in sliding of the wheels. This function is performed by the control valve device |24, the diaphragm |63 of which is subject to the pressure of fluid in the chamber |65, which pressure is gradually increased in accordance with the decreasing speed of rotation of the wheel and axle assembly, as hereinbefore explained. With the spring |56 already subjected to the opposing pressure of the fluid acting in the chamber |48 against the diaphragm |56, the control pressure acting on the diaphragm |63 finally becomes effective to move the diaphragm, follower member |6|, stem |60 and valve element |50 upwardly, whereupon fluid under pressure is vented from the brake cylinder chamber |30 to the atmosphere by way of the pipe |49, chamber |48, past the unseated valve, and through chamber |52 and port |53. The brake cylinder piston |32 is thereby relieved of a portion of the fluid pressure previously acting thereon and the brakes are consequently released sufficiently to permit continued rotationl of the wheels. The degree of reduction inbrake cylinder pressure thus effected is determined by the force exerted by the spring |56, which is adapted to force the diaphragm |58 downwardly and thus to seat the valve element |50 when the desired amount of fluid under pressure has been vented from the brake cylinder chamber.

It will be understood that during this operation, the pressure of fluid in the chamber |43 of the cut-off valve device, which communicates with the conduit |61, is effective through the medium of diaphragm |42 and follower member |44 to hold seated the diaphragm valve |39, so that further supply of fluid under pressure from the brake controlling valve device, not shown, to the brake cylinder is prevented. Full release of the brakes may of course be effected through the medium of the brake controlling valve device at any time, since back ow of communication from the brake cylinder chamber |30 may be established by way of the check valve I 4 When the combined pressures of fluid in the chamber |65 acting on diaphragm |63 and that of brake cylinder uid in the chamber |43 acting on diaphram '|58 are no longer sucient to overcome the spring |56, the valve |50 is moved to the seat |54, and further reductions in brake cylinder pressure can thereafter be effected only by release operation of the brake control valve device associated therewith.

It will be understood, of course, that the speed responsive control valve device |24 may be designed to function for effecting quick release of the brakes in response to slipping of the wheel, and then to cause reapplication of the brakes after the rotative speed of the wheel has been restored to vehicle speed, in a manner similar to that in the case of the equipment shown in Fig. 1.

When the pressure of fluid in the brake cylinder chamber |30 and in the diaphragm chamber |84 of the device |24 communicating therewith has been reduced sufficiently, the spring |82 becomes effective to shift the follower member |80 to the right while the spring |15 is enabled tomove the valve element |10 to its seat. Further supply of fluid under pressure from the reservoir |22 to the conduit |61 is thus cut off to avoid unnecessary loss.

Apparatus shown in Fig. 6

Features of the invention may be embodied in still another form of speed controlled brake apparatus as shown in Fig. 6 of the drawings, wherein are included a brake cylinder device 230, a control valve device 23| which corresponds to the device |24 shown in Fig. 3, and a speed responsive governor mechanism adapted to control the pressure of fluid in a conduit |61ar and which is illustrated in fragmentary form and designated by the character |25, it being understood that the construction of the governor mechanism is the same as that shown in Fig. 3.

The brake cylinder device 230 comprises a cylinder having slidably mounted therein a piston 235, on one side of which is formed a chamber 236 communicating with a supply pipe 231 and on the other side of which is provided a normally vented chamber 238 communicating with a pipe 239. The piston 235 is adapted for operation to apply the brakes upon an increase in the pressure of fluid in the chamber 236. A spring 240 is provided for urging the piston 235 to release position as shown in the drawings.

The control valve device 23| comprises a casing structure having formed therein an inlet chamber 24| communicating by way of a pipe 242 with the supply port of the usual brake controlling valve device, not shown, and having loosely fitted therein a piston 243, which is subject to the opposing pressures of fluid in the chamber 24| and of a spring 244, which is interposed between the piston and the wall of a chamber 245 communi'- cating past the piston with the chamber 24|. The piston 243 is slidably mounted on a stem 241, one end of which isI engaged in a bore 248 formed in the wall of the chamber 245, and the other end of which terminates in a valve 250 which controls communication from the chamber 24| to a passage 25| having a restricted portion 252. A coil spring 254 is interposed between the piston 243 and a collar 255 formed on the stem adjacent the valve 250 for urging the valve into its seated position, as shown in the drawing. A pin 256 is transversely mounted on the stem 241 within the chamber 245 and is adapted to be engaged by the piston 243 upon movement thereof against the force of the spring 244, as hereinafter explained.

Formed in a central section 260 of the casing structure of the device 23| is a valve chamber 26|, which communicates with the brake cylinder pipe 231, and which also communicates with the chamber 245 by way of an opening defined within an annular seat rib 252. The end of the chamberv 23| opposite the seat rib 262 is enlarged to form a bore within which is slidably mounted a piston 265, which is subject at the outer side to the pressure of fluid in a chamber 266 communicating with the passage 25|, and is provided with a restricted port 261 forming communication between the chamber 266 and the valve chamber 26|.

'I'he piston 265 has a stem 269 extending through the chamber 26| and terminating in pin 210 projecting into the chamber 245, on which pin is slidably mounted a valve member 212 disposed in cooperative alignment with the annular seat rib 262. The valve member 212 is adapted to be engaged by a stop shoulder 214, formed at the juncture of the pin 210 with the stem 269, under the pressure of the coil spring 215 which is interposed between the valve member and a transversely disposed pin 216 carried on the outer end of the pin 210. The valve member 212 is thus yieldingly urged toward the seat rib 262 by the force of the spring 215, but is normally adapted to be held in an unseated position as shown in Fig. 6 under the force exerted on the piston and the stemv 269 by a coil spring 211 which is interposed between a recessed surface of the piston 265 and the wall of the chamber 266. If desired, a cap or cover member 218 may be secured to the valve member 212 for enclosing the pin 218 and spring 215, and thus preventing any leakage of fluid under pressure from the chamber 245 to the chamber 261 by way of the bore in the valve member within which the pin 218 is mounted.

Mounted on a valve seat formed on the lower wall of the chamber 261 is a slide valve 288, which is operatively interposed between piston 265 and a lug 281 carried by the stem 269, and which has movably mounted on the upper surface thereof a graduating valve 282 that is disposed within a recess formed in the stem.

The chamber 245 within the casing structure of the device 231 communicates by way of a passage 285 with a valve chamber 286 having disposed therein a feed valve element 281, which isI normally urged toward seated position as shown in the drawing by the force of a spring 288. The feed valve element 281 has a uted stem 298 slidably mounted in a bore 291 forming communication between the valve chamber 286 and a diaphragm chamber 292, through which chamber the end of the stem 298 extends into seating engagement with a diaphragm 293. The diaphragm 293 has a central aperture for receiving the lower end of the stem 298, and has disposed at the side thereof opposite the chamber 292 a follower 296, which is adapted to be urged upwardly by the force of a spring 291 interposed between the follower member and the outer wall of a chamber 298 communicating with the atmosphere througha passage 299. The lower end of the stem 298 is adapted normally to close communication between the chamber 292 and the vented chamber 298, which communication may, however, be established by way of a passage 295 in the follower member in the event of excessive displacement of the diaphragm 293 in opposition to the pressure of the spring 291. The chamber 292 communicates by way of a restricted passage 381 with the conduit 161a leading to the control pressure governor mechanism 125, and also communicates by way of a passage 382 and past a ball check valve 383 with the valve chamber 261.

The control valve device 231 further comprises a casing section 385 having formed therein a valve chamber 386 within which is disposed a valve element 381 which is adapted normally to be held in engagement with a seat 388 under the force of a coil spring 318 transmitted through the medium of a follower element 311 and a diaphragm 312 that is subject to the pressure of uid threaded engagement with the casing structure,

the spring being interposed between the cap nut and the follower member 311. The valve element 381 is adapted to control communication from the chamber 386 through a bore 389 with a volume chamber 315, with the slide valve 288 in the normal position as illustrated, is vented to the atmosphere by way of a port 316 in the slide valve and an exhaust port 311 in the casing.

For operating the valve element 381 there is provided a diaphragm 318 which is clamped withing the casing structure between the normally vented chamber 315 and a pressure chamber 328, the latter communicating by way of a restricted passage 319 with the conduit 161a and also thro-ugh a passage and conduit 321 with a port 322 in the seat of the slide valve 288. The valve element 381 has a uted stem 323 extending through the bore 389 and into engagement with a follower plate 324 which rests against the diaphragm 318 within the chamber 315.

In operation, when an application of the brakes is to be effected, the brake control valve device or triple valve device, not shown, with which the apparatus shown in Fig. 6 is associated, is operated in the usual manner to supply fluid under pressure through the pipe 242 to the chamber 241 of the control valve device 231, from which chamber uid under pressure is free to flow past the loosely fitted piston 243, through the chamber 245, past the valve member 212, and thence by way of the valve chamber 261 and brake cylinder pipe 231 to the piston chamber 236 of the brake cylinder device 238. The brake cylinder piston 235 is thereby operated against the force of the spring 248 to effect application of the brakes against the wheels in the usual manner.

At the same time, fluid under pressure thus initially supplied to the chamber 241 of the control valve device 231 is momentarily effective to force the piston 243 outwardly against the pressure of the spring 244, and the piston is thereby moved into engagement with the pin 256 for operating the stem 241 to unseat the valve 258,

so that fluid under pressure is supplied through' the passage 251 through the piston chamber 266 rapidly enough toprevent the increasing pressure in the valve chamber 261 from causing movement of the piston 265 against the force of the spring 211.

Fluid under pressure supplied to the chamber 245 also flows therefrom by way of the passage 285, chamber 286 and past the normally unseated valve 281 to the diaphragm chamber292, from which fluid under pressure is fed at a controlled rate by operation of the diaphragm 293 and feed valve 281 through the restricted passage 381 to the conduit 161a leading to the pressure governor mechanism 125 associated with the wheel and axle assembly. If the pressure of fluid in the chamber 292 is increased aboveva predetermined value, the spring 291 is adapted to permit movement of the diaphragm 293 downwardly as viewed in the drawing, so as to permit the spring 288 to move the valve 281 into seated position for cutting off flow of fluid under pressure to the chamber 292 until the pressure therein is again reduced by continued operation of the mechanism 125 as already explained. It will thus be understood that the Valve 281 is adapted to be operated as a feed valve to supply uid under pressure at a relatively constant rate to the conduit 161a, which conduit is in turn vented to the atmosphere by reason of operation of the mechanism 125 at a rate determined by the speed of operation of the wheel and axle assembly, so that the pressure of fluid in the conduit is substantially proportional to the speed of the vehicle.

Fluid at the pressure of that in the conduit 161a also acts in the chamber 328 against the diaphragm 318, while at the same time fluid under pressure supplied from the piston chamber 266 through the passage 313 to the chamber 386 acts against the diaphragm 312 in opposition to the force of the spring 310. As already explained, the fluid pressure in the conduitl 161:1 and in the pressure chamber 320 gradually increases as the speed of the associated wheel and axle assembly is decreased due to the effect of the application of the brakes, and as a result, the diaphragm 318, follower member 324 and stem 323 are nally moved upwardly to lift the valve element 301 slightly away from the seat 308, thereby initially releasing fluid under pressure from the piston chamber 266 by way of the passage 313, chamber 306, bore 303, chamber 315 and ports 316 and 311.

Assuming that the retardation of the vehicle is at this time accomplished at a normal rate, the resultant increase in the pressure of fluid established in the diaphragm chamber 320 is such as to cause operation of the valve element 301 as just explained to vent fluid under pressure to the atmosphere from the chamber 266 at a relatively slow rate, sothat the brake cylinder pressure in chamber 261 is rendered effective to shift the piston 265, stem 239 and valve member 212 carried thereby against the pressure of the spring 211 until the valve member is brought into engagement with the seat rib 262, in which position the spring 215 is adapted to resist further movement to the left as viewed in the drawing. In this position of the valve member 212, communication from the chamber 2115 to the chamber`261 and thence to the brake cylinder is cut off, so that further increase in brake cylinder pressure is thereby prevented. While the various parts of the apparatus remain in the position just described, the pressure of fluid in the brake cylinder chamber 236 and in the connected valve chamber 26| of the control Valve device is gradually reduced by flow of fluid to atmosphere through the restricted passage 261 in the piston 265, the chamber 266 and the other communications hereinbeiore pointed out, this reduction in brak cylinder pressure being effected at a rate corresponding with the continued deceleration of the vehicle under normal conditions.

If the rate of deceleration of the Vehicle should be such as to cause a more rapid increase in the pressure of uid in the pressure chamber 320, but yet not at such a rate as might accompany a wheel sliding condition, the diaphragm 31S is adapted to be moved upwardly to unseat the valve element 301 for Venting fluid under pressure from the piston chamber 266 quickly enough to cause the fluid pressure in chamber 26| to shift the piston 265 farther to the left as viewed in Fig. 6, so that a port 330 in the graduating valve 282 is brought into registration with the port 316 of the main slide valve 280. With the elements in this position, the supply of fluid under pressure to the brake cylinder device is cut off by the seated valve element 212, while fluid under pressure is discharged from the brake cylinder by way of the valve chamber 261, ports 330 and 316 and atmospheric port 311, thus effecting a quick partial release of the brakes to limit the effective braking force to a safe value With respect to the vehicle speed. It is normally to be expected that the reduction of uid pressure in the brake cylinder device and in the chamber 261, as just eX- plained, will continue for a relatively short time, since the reduction in the pressure of uid in the chamber 261 below that in the chamber 266 quickly results in return movement of the piston 265 and graduating valve 282 to prevent further venting by way of the communication controlled thereby, after which the fluid under pressure in the brake cylinder can ilow to the atmosphere only through the restricted passage 261 in the piston 265, as explained in the foregoing paragraph.

It will be understood that the reduction in brake cylinder pressure, effected as just described, is not continued after a predetermined low pressure of brake cylinder fluid has been reached, which predetermined brake cylinder pressure is attained when the reduced pressure of fluid in the diaphragm chamber 306 of the control valve device, together with the fluid pressure acting in the chamber 320 against the diaphragm 318, are no longer effective to overcome the force of the spring 310, which is then enabled to force the valve element 301 against the seat 308. It will be remembered, of course, that the feed valve element 281, diaphragm 203 and spring 291 are cooperative to limit the maximum pressure attainable in the conduit 16'1a. So long as the brakes are not released through the medium of the triple valve or other brake controlling valve, not shown, or in other words, While uid under pressure is still supplied by way of the pipe 242, at least the minimum pressure of uid in the brake cylinder as above referred to is maintained therein regardless of leakage, since the ball check valve 393 is adapted to permit flow of fluid under pressure from the diaphragm chamber 292 and through the passage 302 bypassing the closed valve element 212 to the chamber 261 and thence the brake cylinder chamber 236.

It will further be understood that if it is desired to eiTect the release of the brakes by release operation of the usual triple Valve or brake control valve device associated with the apparatus shown in Fig. 6, following operation of the valve member 212 of the control valve device 231 as hereinbefore explained to cut oil communication between the chambers 261 and 245, such release operation may readily be accomplished by establishing communication from the inlet pipe 242 to the atmosphere in the usual manner. With the pipe 242 and the chamber 2M connected thereto suddenly vented to the atmosphere, the higher pressure of fluid in the chamber 245 quickly shifts the piston 21%3 to the left in opposition to the spring 254 for establishing communication of large ilow area between the chamber 2115 and chamber 241 past a recessed wall 333, while the iiuid pressure in chamber 261 acts on the large area of the valve element 212 to move the latter away from its seat 262 against the force of the spring 215. Fluid under pressure thereupon quickly vented from the brake cylinder chamber 236 by way of the communications hereinbefore designated, and upon the consequent reduction in the fluid pressure in chamber 261, the piston 265 and elements operated thereby are returned to the normal position illustrated.

Let it now be assumed that, with the vehicle traveling along the track, fluid under pressure is supplied in the usual manner through the pipe 242 and the various communications hereinbefore traced in the control valve device 231 to the brake cylinder pipe 231 and chamber 236 at such a rate as to effect application of too great a braking force to the associated wheel and axle assembly,

thereon. According to the invention, however, the control valve device 23| is adapted to respond to an initial slipping of the wheels to 'effect the quick release of the braking force applied thereto for thereby restoring the normal rotation of the wheels before sliding occurs.

Referring again to Fig. 6, let it be assumed ,that in effecting an application of the brakes fluid under pressure has been supplied in the usual manner to the pipe 242, chambers 24| and 245, past the unseated cut-oil valve 212, and through the chamber 26| and pipe 231; to the brake cylinder piston chamber 236, and that the pressure of fluid supplied to the conduit |61a by way of the feed valve 281 and associated elements is increased above the normal pressure, due to a too rapid deceleration of the associated wheel and axle assembly with respect to the vehicle speed. When the pressure of fluid in the diaphragm chamber 32D communicating with the conduit |61a. is thus built up to a relatively high value, it becomes effective through the medium of the diaphragm 318, follower member 324'and stem 323 to move the valve element 301 to its uppermost position, it being understood that the uid pressure already supplied to the chamber 306 acts on the diaphragm 3|2 partly to overcome the downward force of the spring 3|0, with the result that uid under pressure is quickly dise charged from the piston chamber 266 to the atmosphere by way of the passage 3 3, chamber306, past the unseated valve member 301, and thence through the chamber 3|5, and ports 3|6 and 3|1.

Since the reduction of pressure in the fluid in chamber 266 is thus effected at a ratevfaster than that caused in the chamber 26| by flow of uid through the restricted port 261 in the piston 265, the piston is shifted to the left against the opposing force of the spring 211 until the slide valve 280 operated thereby is moved far enough to uncover the port 239. With the .port 239 uncovered, fluid under pressure is admitted from the chamber 26| by way of the port and pipe239 to the chamber 238 of the brake cylinder device 230, so that the iiuid pressures acting on opposite sides of the brake cylinder piston 235 are quickly equalized for effecting a prompt release of the brakes. The wheel and axle assembly is thereby relieved of braking force in time to prevent wheel sliding.

Shortly after movement of the piston 265 to effect release of the brakes, as just explained, the spring 3|0 becomes effective to force the follower member 3| and diaphragm 3| 2 downwardly against the reduced'fluid pressure in the chamber 306, thereby seating the valve member 301. The gradual iiow of fluid under pressure from the chamber 26| through the restricted port 261 in the piston to the chamber 266 then cause's'the pressure therein to increase until the spring 211 is enabled to shift the piston and the slide valve 280 back to lap position, wherein the chamber 238 of the brake cylinder device is connected, to the atmosphere through the pipe and port 239, and ports 3|6 and 3|1, while the cut-offvalve member 212 remains seated on the rib 262assuming that the supply of fluid under pressure to the chamber 245 has not meanwhile been cut od by release operation of the usual brakecontrolling valve or triple valve device, notV shown. rIt will thus be apparent that reapplication ofthe brakes is effected following the quick release thereof, such reapplication of the brakes being eiected by the iiuid under pressure remainingn the brake cylinder chamber 236 and acting on the piston 235. It is preferred that the parts'be so designed and adjusted that the full force of 'the reapplication does not become effective until the wheel rolls at non-slipping speed. Y f

Summary governed by a control pressure that is predetermined by the rate at which fluid is vented Vby periodic operation of a wheel actuated valve device, I have provided control apparatus operable entirely by fluid under pressure vand sensitive to an initial wheel slipping condition gfor ensuring quick release of the braking force intime to prevent wheel sliding. It will be understood that structural details of each of the three embodiments of the invention hereinbefore described may be 'modified and adapted for association with variousforms of fluid pressure brake apparatus, and that it is not intended to limit the scope of the invention to the embodiments disclosed herein or otherwise than by the scope of the appended claims.

Having now described my invention,what I claim as new and desire to secure by Letters Patent is: v Y

1. Speed responsive control apparatus for association with brake cylinder means voperable to apply braking force to a wheel, comprising valve means operative to vary the maximum limit of fluid pressure attainable in the brake cylinder while an application of the brakes is effected, means responsive to a predetermined increase in brake cylinder pressure for establishing a control pressure," means responsive to an increase in said control pressure for operating said valve means to reduce the pressure of uid in the brake cylinder, and means operative in accordance with the rotative speed of the wheel for governing said control pressure.

2. Speed responsive control apparatus for association with brake cylinder means operable to apply braking force to a wheel, comprising valve means operative to vary the maximum limit of fluid pressure attainable in the brake cylinder,v fluid supply means operable when an application of the brakes is effected tol maintain a substantially constant flow of fluid under pressure to 'a communication, means o-perable to bleed away iluid thus supplied to the communication at'a rate varying in accordance With the rotative speed of the wheel for thereby governing thepressure of the fluid, and means responsive to said governed fluid pressure for operating said valve means.

3. In a speed responsive contro-l apparatusA adapted for association with brake cylinder means operable to apply braking force to a Wheel, in combination, valve means operative to vary the maximum limit of pressure attainable in the brake cylinder, fluid supply means operable when an application of the brakes is effected to maintain a substantially constant flow of fluid under,

pressure to a communication, means operative by the wheel for periodically withdrawing` measured quantities of fluid thus supplied lto thecom.- munication for thereby governing the fluidpres-v sure in accordance with the rotative speed ofthey wheel, and means responsive to said governed fluid pressure for operating said valve means.

4. Speed responsive control apparatus for a brake equipment operable to apply braking force to a vehicle Wheel, comprising mechanism operative to vary the maximum limit of braking force attainable in operation of said brake equipment While an application of the brakes is effected, means responsive to a predetermined increase in braking force for establishing a control uid pressure, means responsive to an increase in said control pressure for operating said mechanism to reduce the braking force attainable, and means operative in accordance with the rotative speed of the wheel for governing said control pressure.

5. Speed responsive control apparatus for association With brake cylinder means operable to apply braking force to a Wheel, comprising valve means operative to vary the maximum fluid pressure attainable in the brake cylinder, fluid supply means operable when an application of the brakes vis effected to maintain a substantially constant oW of fluid under pressure to a communication,

means responsive to the fluid pressure in said communication for operating said valve means, an element rotatable With the wheel and having one o r more normally vented chambers opening at aface thereof, and a stationary member in sliding engagement therewith and having a port through which fluid flowing from said supply means to 'said communication is intermittently discharged to said chambers according to the rotative speed of said element.

6. Speed responsive control apparatus for association with brake cylinder means operable to apply braking force to a Wheel, comprising valve means operative to vary the maximum fluid pressure attainable in the brake cylinder, fluid supply means operable when an` application of the brakes is effected to maintain a substantially constant flovvof fluid under pressure to a communication, means responsive to the fluid pressure in said communication for operating said valve means, an element ro-tatable with the Wheel and having one or more normally vented chambers opening at a face thereof, a stationary member in sliding engagement therewith and having a port throughvvhich fluid `flowing from said supply means is intermittently discharged to said chambers according to the rotativey speed of said element, and means yieldingly urging said-element and member together.

7. Speed responsive control apparatus for association with brake cylinder means operable to apply braking force to a Wheel, comprising valve means operative to vary the maximum fluid pressure attainable in the brake cylinder, iiuid supply means operable when an application. of the brakes is effected to maintain a substantially constant iloW of fluid under pressure to a communication, means responsive to the fluid pressure in said communication for operating said valve means, an element'rotatablewith the Wheel and having one or more normally vented chambers opening at .a face thereof, and a stationary member composed of self-lubricating carbonaceous material in sliding engagement Withsaid faceand having a port through which fluid flow- Y ingV from. said supply means through said communication iS intermittently discharged to said chambers according to the rotative speed of saidelement.

8. Speed responsive. control apparatus adapted for association with brake cylinder means operable to apply braking forceto a Wheel and axle in said chamber for operating said valve means,

a rotary element carried by the axle having a plurality of normally vented cavities opening at a bearing face thereof, and a non-rotating memy ber mounted in sliding relation with the bearing face of said element and'having a port adapted to establish communication from saidchamber to said cavities in succession for thereby varying the fluid pressure in the chamber according to the rotative speed of the Wheel and axle assembly.

9. Automatic brake control apparatus adapted to be associated With brake cylinder means operable to apply braking force to a wheel, comprising means operative upon a predetermined increase in thepressure of uid in said brake cylinder means to establish a control fluid pressure varied inversely in accordance With the rotative speed of the Wheel, fluid pressure responsive means subject to said control pressure, and valve means adapted for operation by said pressure responsive means upon a sudden increase of predetermined degree in said control pressure for quickly venting uid under pressure from said brake cylinder.

10. Automatic brake control apparatus adapted to be associated with brake cylinder means operable to apply braking force to a Wheel, comprising means operative by fluid under pressure supplied to the brake cylinder to establish a control fluid pressure varied in accordance With the rotative speed of the Wheel, said control pressure gradually increasing substantially in proportion to a gradual reduction in Wheel speed, fluid pressure responsive means subject to said control pressure, and valve means adapted for operation by said pressure responsive means upon a sudden increase of predetermined degree in said control pressure for quickly venting fluid under pressure from said brake cylinder.

11. In a iiuid pressure brake equipment for a Wheeled vehicle including a brake cylinder adapted to be supplied with fluid pressure for effecting an application of the brakes, in combination: fluid pressure responsive control valve means operable to cut off the supplyof fluid under pressure to the brake cylinder and to vent fluid under pressure therefrom for reducing the braking force appliedV thereby, fluid pressure responsive feed valve means operative upon'a predetermined in` crease in brake cylinder pressure to effect a subed to bel suppliedfwith iiuid under pressure for.

eiecting an application of the brakes, in combi..-

nation: casing. means providing a control pres-v sure chamber, fluid pressure responsive feed valve means operable to eiect a substantially constant` supply of iluid under pressure to said chamber, uid pressure governor means operative by a wheel of the vehicle to effect intermittent withdrawal of fluid under pressure from said chamber for varying the fluid pressure therein in proportion to the vehicle speed, control valve means operable to cut off the supply of fluid under pressure to the brake cylinder and to vent fluid therefrom for reducing the braking force applied thereby, a spring, and movable abutment means subject to the opposing pressures of lluid in said chamber and of said spring for actuating said control valve means.

13. In a iiuid pressure brake equipment for a Wheeled vehicle including a brake cylinder adapted to be supplied with uid under pressure for effecting an application of the brakes, in combination: casing means providing a control pressure chamber, fluid pressure responsive feed valve means operable to effect a substantially constant supply of fluid under pressure to said chamber, control pressure governor means operative by a Wheel of the vehicle to eifect intermittent withdrawal of fluid under pressure from said chamber for varying the uid pressure therein in proportion to the vehicle speed, control valve means operable to cut off the supply of fluid under pressure to the brake cylinder and to vent fluid therefrom for reducing the braking force applied, a volume chamber formed in said casing means, a spring disposed therein, and a movable abutment having a restricted port and subject on one side to the pressure of said spring and of fluid in said volume chamber and on the opposite side to the uid pressure in said control chamber, said abutment being operative upon a sudden variation of control pressure to cause unseating of said control valve means for a limited interval, Whereby the brakes are quickly reduced to prevent Wheel sliding and then conditioned for a reapplication.

14. In a fluid pressure brake equipment for a Wheeled vehicle, in combination, a brake cylinder having piston means operative under the pressure of fluid supplied at the application side thereof to apply the brakes and upon supply of fluid at the opposite side of said piston to release the brakes, casing means providing a control chamber, fluid pressure responsive feed valve means operable by fluid under pressure supplied at the application side of said piston means to effect a substantially constant supply of ud und-er pressure to said chamber, fluid pressure governor means operative by a Wheel of the vehicle to effeet intermittent Withdrawal of fluid under pressure from said chamber for varying the pressure of uid therein in proportion to the vehicle speed, and fluid pressure responsive control valve means operative upon a sudden variation in lluid pressure in said control chamber to establishcommunication through which fluid at the application side of said brake cylinder piston means can ow to the opposite side thereof for quicklyeffecting the release of the brakes.

15. In a fluid pressure brake equipment for a Wheeled vehicle, in combination, a brake cylinder having piston means operative under the pressure of uid supplied at the application side thereof to apply the brakes and upon supply of fluid at the opposite side of said piston to release the brakes, casing means providing a control chamber, fluid pressure responsive feed valve means operable by fluid under pressure supplied at the application side of said piston means to elect a substantially constant supply of fluid under pressure to said chamber, uid pressure governor means operative by a Wheel of the vehicle to effect intermittent withdrawal of fluid under pressure from said chamber for varying the pressure of fluid therein in proportion to the vehicle speed, and fluid pressure responsive control valve means operative upon a sudden variation in uid pressure in said control chamber first to establish communication from the application sidev of said brake cylinder means to the opposite side thereof and then to cut o said communication While venting uid under pressure from said opposite side.

BURTON S. AIKMAN. 

